Endotoxic shock was studied in the sheep in an effort to develop a model which was similar to this pathophysiologic state in humans. E. coli endotoxin was administered to ewes which had previously had catheters implanted in them for the recording of cardiopulmonary and renal data. Results indicate that the sheep model may show the high flow, low resistance shock state often reported in man. A biphasic response is seen in arterial blood pressure, with an early fall from 1/2 to 1-1/2 hour, and a second decline from 4 to 6 hours. The early fall is accompanied by a drop in systemic resistance while the later decline is accompanied by only a slight increase in resistance. Pulmonary arterial pressure (PAP) and pulmonary resistance show a momentary marked increase. PAP decreases from 1/2 to 2-1/2 hours and then shows an increase for the duration of the experimental time period. Arterial pO2 values showed a significant decrease during the first 2 hours indicating a possible alveolar capillary block. Minute volume increases are significant during the first 3 hours and remain elevated during the entire six hours. Interpretation of renal data is complicated by early renal shutdown resulting in no urine production and low glomerular filtration rates.